Process of combustion of liquid fuel



Nov. 15, 1927.

E. G. HODGES PROCESS OF COMBUSTION OF LIQUID FUEL 2 Sheets-Sheet 1 Q Filed Oct. 26, 1925 I,(P4LH96 E.G.HODGE$ PROCESS OF COMBUSTION 0F LIQUID FUEL Filed Oct. 26,,1925 2 $heets-heet 2 said view being Patented Nov. 15, 19 27.

PATENT OFFICE."

EDWARD HODGES, OF MILWAUKEE, WISCONSIN.

PROCESS OF COMBUSTION OF LIQUID FUEL.

Application filed October 26, 1925. Serial No. 64,853.

This invention relates to theart of liquid fuel burners for heating furnaces; and pertains more particularly to liquid fuel burners as employed in domestic heating installations.

One of the principal objects of the invention is to provide methods for checking the noise and vibration incident to the operation of such burners, especially when the latter are employed in domestic heating or other installations, where the noise and vibration has been heretofore one of the greatest defects in the operation of liquid fuel burner equipment.

In addition to the improvement as above stated, the invention provides substantial economies in the operation of liquid fuel burner equipment; and the invention has for further objects such other improvements relating to the liquid fuel burner art, as will be found to obtain in the structures and methods hereinafter described or claimed.

An apparatus for carrying out the methods of checking noise and vibration isdisclosed and claimed in my co-pending application, Serial N 0. 602,562.

In the accompanying drawings forming a partof thisspecificationand showing for purposes of exemplification one form of construction in which the invention may be embodied and practised, but without limiting the claimed invention to such illustrative instance or instances.

Fig. 1 is a side elevation of a domestic heating furnace of conventional type provided with one form of apparatus embodying and for practising the improvements of the invention;

Fig. 2 is an enlarged fragmentary view, partly in verticalsection and partly in side elevation, taken through Fig. 3 on the plane of the line 2-2 and illustrating the construction of an air-preheater which may be employed in conjunction with such apparatus.

Fig. 3 is an end view of the air-preheater taken on a plane indicated by the line 3-3 of Fig. 2;

Fig. 4 is an enlarged detailed view of the firepot or atomization and gasification chamber, and the liquid fuel burner apparatus, partly in horizontal section and partly in plan and taken through Fig. 1 on the plane of the line 4- 4; an

view taken through Fig. 1 on the plane of the line 5-5.

Referring to the drawings:

There is shown at 6 a domestic heating furnace of any desired type of construction, to which the invention may be applied. In fact, because of the important result of reducing the noise and vibration, as accomplished by the invention, a domestic heating furnace constitutes one of the most important applications of the invention. The exhaust or waste gases from the said furnace pats out through the furnace flue 8, and subsequently are discharged into the chimney or stack 7 by way of the stack flue 9.

According to the present form of apparatus, the waste or flue gases from the furnace are conducted through an air-preheater before being delivered to the stack flue 9. This air-preheater 10 is constructed in the form of a cylinder which is closed at one end, as at 11, but is only partially closed at its other end by the plate 12. This plate covers only the lower portion-of the cylinder, so there is provided an inlet 13 for the combustion-supporting air at that end of the cylinder adjacent to plate 12. Adjacent to the other end of the cylinder 10, an outlet 14 for said combustion-supporting air leads from the top of the cylinder into ,the airsupply pipe 25.

Positioned within the cylinder 10 are two partitions or tube-plates 15, which divide the interior of said cylinderinto a large cenchamber 16 and also the stack fine 9, both flues 8 and 9 terminating within said chamber 16 below the lowermost'tubes 19. These lowermost tubes 19 are preferably positioned slightly .above the top of the end plate 12.

With the above described construction, the

hot waste gases from the furnace are discharged b the furnace fine 8 into the central cham er 16 and circulate in heat-ex changing relation with the combustion-supporting air passing through the tubes 19, before said waste gases pass through the stack flue 9 into the furnace stack 7. Consequently, the combustion-supporting air may be preheated before being delivered to the liquid fuel burner apparatus. The recuperative effect thereby produced acts to promote economy in the use of fuel and to mcrease the heating efficiency.

If desired, the bottom portion of the tank, including all three compartments, 16, 17 and 18 may be filled with water, or other liquid, as shown in Fig. 2. The water is maintained at a level slightly below the top of the end plate 12 and the upper ends of the flues 8 and 9 within the central chamber 16. Near their bottoms, the tube plates 15 are provided with openings 39 which permit circulation of the water through the three chambers of the tank. The use of water in the tank 10 supplies moisture to the air, increasing the efficiency of the mixture supplied to the burner equipment, and also acts to precipitate solid foreign matter, including dust particles and the like from the air.

The liquid fuel burner apparatus, as shown in the drawings, contemplates the employment of a double burner equipment and, for convenience, the invention will be described in conjunction therewith. This double burner equipment provides a relatively small burner unit which may be operated constantly as a pilot for the larger unit and also when only a low heating effect is required, and a larger burner unit operated when a higher or the maximum heating eli'ect is necessary. The larger burner unit may be controlled in its operation by any suitable thermostatic means, which however is not shown in the drawings. Each burner unit is intended to be operated with any usual grade of fuel oil, or any other suitable liquid fuel.

Located within the furnace 6, is a firepot or chamber 21, open at its top, as shown in Fig. 1, to the interior of the furnace. This firepot provides an enclosed zone relatively restricted in respect of the furnace chamber into which the liquid fuel may be discharged, or sprayed, for gasification, as will be explained hereinafter. -The smaller burner unit, which may be termed, for convenience, the pilot unit, includes a burner pipe 22, one end of which extends into the bottom of the firepot 21 and the other end of which is connected with the outlet of a fan or blower 23. The inlet of said blower 23 is connected by a supply pipe 24 with the airsupply pipe 25. The air supply pipe 25, as heretofore explained, may receive the combustion-slipporting air from the outlet 14 of the air preheater chamber 18, as shown in Fig. 2. The interior of the burner pipe 22 is provided with a venturi of ordinary confi uration, as illustrated by dotted lines in Fig. 4. A liquid fuel supply duct 29 communicates with the interior of the venturi in said burner pipe 22, at the point of maximum constriction of the venturi, whereby the combustion-supporting air fed through the pipe 22 by the blower 23 draws liquid fuel into the firepot 21, as shown in Fig. 4, and the other end of said pipe 33 with the outlet of a blower 34. The supply pipe 25 for the com bustion-supporting air leads directly into the inlet of the blower 34, as shown in Fig. 1. The interior of the burner pipe 33 is also provided with a venturi (see Big. 4). A plurality of feed ports 35 connect the interior of the burner pipe 33 atthe point of maximum constriction of the venturi with a surrounding feed chamber, to which chamber is connected the fuel feed duct 36. This feed duct 36 leads from the fuel supply pipe 31; the supply of liquid fuel-in the duct 36 may be controlled by a suitable valve 37, located in said duct, as shown in Fig. 5. With this construction, the air passing through the burner pipe 33 draws liquid fuel from the duct 36 though the ports 35 and the air and fuel are sprayed into the firepot 21 for gasification, and subsequent ignition, for example, from the pilot burner, which may be kept burning constantly, as above explained.

An important feature of the invention resides in the discovery that by introducing into the zone of gasification of the fuel, in addition to the fuel and combustion-supporting air, a neutral gaseous diluent, for example, any suitable inert gas, or a gas having a low free oxygen content, such as waste gas from the outlet of the furnace itself, the noise and vibration incident to the operation of the burner are checked to such an extent as to be scarcely perceptible, if at all, to the occupants of the dwelling, in which the liquid fuel burner is bein operated; By this discovery, there has lieen eliminated, to all practical purposes this objectionable feature of noise, which has be n heretofore one of the greatest defects in liquid fuel burner equipment, especially when employed for domestic heating installations with the result that there is removed one of the greatest obstacles to the practical employment of ii uid fuel burners for such installations. lhe

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unique result of producing a quiet flame and substantially a noiseless operation may, according to the invention, be produced in various ways and with various mstallations, involving the application of the inert gas or neutral gaseous diluent to accomplish the intended result.

Inasmuch as the present disclosure of apparatus involves the use of the double burner equipment, as hereinbefore explained, and a preheater for heating the combustionsupporting air, the invention may be conveniently explained in conjunction with such pre-heater apparatus and applied to both units of the double burner equipment.

Referring to Fig. 2, a return waste or flue gas pipe connection 27, extends from the air-supply pipe 25 into the top of the central chamber 16 of the air preheater. Through this return waste gas pipe 27, a portion of the waste or flue gas from the furnace, said gas still containing a large proportion of its heat, may be introduced into the air supply pipe 25, so that the air entering both blowers 34 and 23 which respectively feed the large and small burner units has been mixed with a suitable proportion of an inert gas relatively low in free oxygen content. tion of this neutral gaseous diluent, so introduced into the combustion-supporting air for either burner unit may be controlled to give the desired quieting effect to the flame, without excessive dilution of the air-supply, by regulating the butter-fly damper 28 in the return, waste gas pipe 27 As shown in Fig. 1, this damper 28 is positioned in said pipe 27 at a point in advance of where the latter merges into the air supply pipe 25. The neutral gaseous diluent for either unit of the burner equipment, in the present instance, in the form of preheated return waste or flue gas from the furnace, may thus be introduced into the atomization and gasification zone of the fuel, in controlled amount, along with the liquid fuel and combustion-supporting air.

By introducing the neutral gaseous diluent into the gasification zone of the fuel, gasification is promoted. so that the liquid fuel is converted practically into a gas. This zone provided by the firepot or combustion chamber 21, is of substantial volume, but is relatively restricted in respect of the furnace chamber, and said zone is maintained at a relatively low temperature but sufficient to initiate combustion. The introduction of the neutral gaseous diluent has the further effect of retarding combustion of the fuel, with the result-that, although, for example, some ignition may take place within the firepot 21, the main flame zone is spread beyond said firepot, the fuel burning slowly and with flame characteristics and effects somewhat analogous to the burn- :Ihe proper proporing of fuel gas. Moreover, the neutral gas-. eous diluent introduced into the firepot or combustion chamber 21, has the function of retarding combustion I of the liquid fuel prior to the completion of its gasifying stage. Although suflicient combustion in the firepot is allowed to promote complete gasification of the liquid fuel, the diluent gas retards progress of combustion beyond that necessary forthis purpose. The neutral gaseous diluent functions to check rise of temperatures in the gasification zone such as would effect thermal decomposition of the fuel, without retarding the progress of gasification, for example, by keeping the liquid fuel below the cracking temperature, but

above its end point. The result is that the noise and vibration of operation. are checked, so as to be almost imperceptible. .The proportionate amount of the flue gases introduced into the combustion-chamber 21 relatively to the air or fuel may be regulated and controlled to insure the desired silent operation as produced by the functions above described, by operation of the damper 28 in the flue gas pipe 27 to control the supply of flue gas returned from the furnace chamber to the air feed pipe 25 of the burner. The use of a neutral gaseous diluent, as practised in accordance with the invention, also results in increased economy of opera tion and increased heating efliciencyk l' The invention as herein above set forth may be variously embodied and practised within the scope of the claims hereinafter made.

What is claimed is :T r 1. In the art of burning liquid fuel in domestic furnaces, the method of checking noise and vibration, which comprises, spraying and gasifying the li uid fuel in a zone v,

of substantial volume ut relatively restr cted in respect of the furnace chamber, maintaining said zone at a relatively low temperature but suflicient to initiate combustion, introducing into said zone air and a substantially inert gas of relatively low oxygen content and thereby retarding combustion of the liquid fuel in said zone prior to the completion of its gasifying stage, and

burning the combustible mixture adjacent said zone.

2. In the art of burning liquid fuel in domestic furnaces, the method of checking noise and vibration, which comprises, spraying and gasifying the li uid fuel in a zone of substantial volume ut relatively restricted in respect of the furnace chamber, I

maintaining said zone at a relatively low temperature but. sufficient to initiate combustion, introducing into said zone air and a substantially inert gas. of. relatively, low oxygen content. and thereby retarding combustion of the fuel and the resultant rise of temperatures in said zone to avoid thermal pleting the com d'ecomposition of the fuel during its gasification stage, and completing the combustion of the gasified fuel outside of said zone.

3, In the art of burning liquid fuel in domestic furnaces, the method of checking noise and vibration, which comprises, spraying and gasifying the liquid fuel in a zone of substantial volume but relatively restricted in respect of the furnace chamber, maintaining said zone at a relatively low temperature but sufiicient to initiate combustion, introducing into said zone air and flue gas from said furnace chamber and thereby retarding combustion of the liquid fuel insaid zone prior to the completion of its gasifying stage, and burning the combustible mixture outside of said zone.

4. In the art of burning liquid fuel in domestic furnaces, the method of checking noise and vibration, which comprises, spraying and gasifying the liquid fuel in a zone of substantial volume but relatively restricted in respect of the furnace chamber, maintaining said zone at a temperature but sufficient to bastion, introducing into said zone air and flue gas from said furnace chamber and thereby retarding combustion of the fuel and the resultant rise of temperatures in said zone to avoid thermal decomposition of. the fuel during its asification stage,and comfiustion of the gasified fuel adjacent said zone.

initiate comrelatively low 5. In the art of burning liquid fuel in domestic furnaces, the method of checking noise and vibration, which comprises, introducing the liquid fuel into a zone of substantial volume but relatively restricted in respect of the furnace chamber, maintaining said zone at a relatively low temperature but suflicient to initiate combustion, and introducing into said zone air and a substantially inert gas of relatively low oxygen content, in such proportion as to retard combustion of the fuel in said zone, thereby to avoid thermal decomposition of the fuel and to cause the completion of the combustion of the fuel outside of said zone.

6. In the art of burning liquid fuel in domestic furnaces, the method of checking noise and vibration, which comprises, introducing the li uid fuel into a zone of substantialvolume ut relatively restricted in respect of the furnace chamber, maintaining said zone at a relatively low temperature but sufficient to initiate combustion, and introducing into said zone air and gases from the furnace chamber, in such proportion as to retard combustion of the fuel in said zone thereby to avoid thermal decomposition of the fuel and to cause the completion of the combustion of the fuel outside of said zone.

In testimony'whereof, I have signed my name to this specification.

EDWARD G. HODGES. 

